This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-156481, filed Jun. 3, 1999; and No. 11-213897, filed Jul. 28, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a communication control method for an electronic mail system in which a plurality of electronic mail devices transmit and receive images in the form of electronic mail (hereinafter referred to as xe2x80x9ce-mailxe2x80x9d) over a computer network such as the Internet.
IETF (Internet Engineering Task Force) is an organization which determines the standard regulations of the Internet. The standards determined by the IETF will be opened to the public as RFC. While facsimiles which transmit and receive images over telephone lines are very popular, Internet facsimiles are also known which transmit and receive images over the Internet in stead of the telephone lines. The IETF considered the standardization of Internet facsimiles and established the standards for transmission and reception of images using an e-mail. RFC 2305 fixes conditions for image transmission (the number of horizontal pixels: 1728 pixels, resolution: 200xc3x97100 dpi or 200xc3x97200 dpi and coding system: MH) and defines that an image is converted to a file of the TIFF (Tagged Image File Format) format, attaches this file to an e-mail message according to the MIME (Multipurpose Internet Mail Extensions), the standard e-mail format, and this e-mail message is then transmitted to a designated e-mail address. This specification is for one-sided transmission of an e-mail from a sender to a receiver, which is the same as an ordinary electronic mail system used in personal computers or the like. This system is hereinafter referred to as xe2x80x9cfirst modexe2x80x9d. As apparent from the above, an Internet facsimile can be said to be one kind of electronic mail devices capable of transmitting and receiving images using an e-mail.
In the first mode, the sender cannot know whether or not the transmission destination or receiver has received and processed a transmitted image properly. As only images under the fixed conditions are permitted, it is not possible to transmit images with a higher quality. In this respect, the standards that enable the detection of the capability of a receiver and the confirmation of delivery were set up as RFC 2532. This system is hereinafter referred to as xe2x80x9csecond modexe2x80x9d. At the time an e-mail message attached with a TIFF file is transmitted, a response message from the receiver is requested. This response message is created by using DSN (Delivery Status Notifications) or MDN (Message Disposition Notifications).
Upon reception of an e-mail message attached with a TIFF file, the transmission destination or receiver performs processes, such as displaying the image and printing it, describes the processing result and the local capability in a DSN/MDN message and sends this DSN/MDN message back to the sender. As a result, the sender can confirm the delivery as well as know the receiver""s capability through the DSN/MDN message. The receiver""s capability is used in later image transmission so that images can be transmitted to this transmission destination under the conditions that match the receiver""s capability. When the capability of a receiver is unknown as in the case where, for example, it is the first transmission to that destination, an image under the fixed conditions of the first mode, which can surely be processed by any receiver, should be transmitted.
Even if the receiver supported the second mode, it would be inevitable to send images of the same quality as that allowed by the first mode. One way to solve this problem is to define a capability-requesting e-mail, sends this capability-requesting e-mail to the transmission destination before image transmission, receives a response on the capability from the receiver, and then transmit an image which is matched with the capability.
This method however has the following shortcoming. In a case of transmitting an image to a transmission destination whose capability is unknown, if the receiver is an electronic mail device which has the same capability as the sender, the receiver understands a capability-requesting e-mail, if sent prior to image transmission, and sends back a response on the capability. If a capability-requesting e-mail is sent to an electronic mail device which has ordinary e-mail software installed therein, however, the receiver cannot understand the capability-requesting e-mail so that the subsequent behavior of the receiver is not predictable. That is, interoperability is ruined when a capability-requesting e-mail is sent to an electronic mail device which has ordinary e-mail software installed therein.
Another solution to the aforementioned problem is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-65963, which appends an image file added with capability request information to an e-mail and asks a receiver to return a response before scanning an image, scans an image which is matched with the capability to generate an image file by and transmits an e-mail attached with that image file.
That is, this publication discloses such a technique that when an image file to be attached to an e-mail is a TIFF file, a sender describes a capability request message in a tag (Image Description) which indicates the contents of a TIFF file defined by the TIFF specifications. Then, an e-mail attached with an image file to which a capability request message is added is transmitted to a transmission destination before scanning an original image. In this case, the image file does not include actual image data.
A receiver which has the same capability as the sender receives the image file, and identifies the capability request message added to the image file. Then, like the sender, the receiver describes a capability response message teaching its own reception capability in a tag (Image Description) which indicates the contents of a TIFF file defined by the TIFF specifications. The receiver attaches an image file added with this capability response message to an e-mail and then sends this e-mail to the sender. In this case too, the image file does not include actual image data.
The sender performs such control as to acquire capability information of the transmission destination from the capability response message added to the image file and transmit a scanned original image to the transmission destination in the form of an image file which satisfies the conditions matched with the capability information.
According to this communication control method, in the case of transmitting an image to a transmission destination whose capability is unknown, if a transmission destination is an electronic mail device which has the same capability as the sender, the transmission destination can understand a capability-requesting image file transmitted before image transmission and send back a response indicating the receiver""s capability. If such a capability-requesting image file is sent to an electronic mail device which has ordinary e-mail software installed therein, however, this device cannot understand the capability request or cannot make a capability response, and cannot therefore display or print the image file. As a result, the receiver informs the sender of an error or may hang up in an image-file processing routine in the worst case due to the inadequate file structure of the received image file that contains no actual image data. That is, interoperability to an electronic mail device which has ordinary e-mail software installed therein is ruined.
Accordingly, it is an object of the present invention to provide a communication control method for an electronic mail system, which, in a case of transmitting an image in the form of an e-mail to a transmission destination whose capability is unknown, can guarantee interoperability even if the transmission destination is an electronic mail device which has ordinary e-mail software installed therein, and can detect the capability of the transmission destination if the destination has the same function as the sender and can transmit an image according to that capability.
To achieve the above object, according to one aspect of this invention, there is provided a communication control method for an electronic mail system comprising a plurality of electronic mail devices, wherein an electronic mail device to be a sender adds identification information to an e-mail, attaches an image of specific conditions to the e-mail and transmits the e-mail; when identifying the identification information in a received e-mail, an electronic mail device to be a receiver adds identification information and local capability information to an e-mail to be transmitted and transmits the e-mail; when identifying the identification information in a received e-mail, the electronic mail device to be the sender acquires the capability information from that e-mail, attaches an image matched with the acquired capability information to an e-mail to be transmitted and transmits the e-mail; and the electronic mail device to be the receiver processes the image attached to the received e-mail.
According to this invention, in a case where an image is transmitted in the form of an e-mail to a transmission destination whose capability is unknown, it is possible to guarantee interoperability even if the transmission destination an electronic mail device which has ordinary e-mail software installed therein, and to detect the capability of the transmission destination if the destination has the same function as the sender and transmit an image according to that capability.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.